1. Field of the Invention
The present invention relates to a color filter array and, more particularly, to a color filter array used in a solid-state image sensor used in an imaging device.
2. Description of the Related Art
In recent years, a multiband camera (a multi-spectrum camera) has been proposed in which color filters having different center frequencies are arranged in an array to simultaneously acquire image information and frequency information (a spectral image) of an object. In such a multiband camera, to improve resolution of a frequency to be acquired, it is necessary to arrange a large number of color filters having slightly different center frequencies. However, as types of the color filters are increased, an interval of pixels for acquiring images having the same frequency characteristic is expanded and spatial resolution is deteriorated.
Therefore, a solid-state image sensor is proposed in which characteristics of color filters are variably set to simultaneously improve frequency resolution and spatial resolution. As such a variable color filter, for example, there is a variable color filter disclosed in Japanese Patent Application Laid-open No. 2011-43681.
The variable color filter disclosed in Japanese Patent Application Laid-open No. 2011-43681 is a color filter in which fine metal structures are cyclically arranged to perform wavelength selection making use of surface plasmon. In such a color filter, a dielectric constant variable material such as a ferroelectric substance is used in a dielectric substrate and a refractive index of the ferroelectric substance is changed by voltage application to variably set a filter characteristic.
However, when color filters having different center frequencies are arranged in an array and used in a solid-state image sensor for spectral image acquisition, it is necessary to provide, for each of the color filters, a circuit for voltage application. As a result, an aperture ratio decreases because of the circuit and the transmittance of the color filters decreases. Costs for circuit formation increase.